In the following description, a femto cell is described in brief.
First of all, ‘femto’ indicates a very small unit in scale of 10−15. According to this meaning, a femto cell means an ultra small/low power indoor base station for home/office. Although a femto cell is used with a meaning similar to that of a pico cell, it can be used with the meaning of having a further evolved function. The femto cell is a small cellular base station connected to a broadband router and is able to connect voice and data of 3G system to a backbone network of a mobile communication carrier provider via DSL link and the lie as well as voice and data of the conventional 2G system.
Advantages of the above-described femto cell are described as follows.
First of all, ongoing attention is paid to the recent research report announcing that a femto cell can trigger the acceleration of the 3G propagation and the extension of an indoor coverage. The estimated number of global femto cell users will be incremented up to 102,000,000 until 1011 and the estimated number of APs (access points, i.e., base stations) will reach 32,000,000 by then.
And, a femto cell is able to reinforce a cell coverage and is also able to enhance quality of voice service. Moreover, mobile communication carriers are expected to provide services via femto cells to enable subscribers to fully adapt to 3G.
In particular, a communication system via femto cell is able to enjoy the following advantages: (1) Cell Coverage Improvement; (2) Infrastructure cost decrease; (3) New service Offering; (4) FMC (Fixed Mobile Convergence) acceleration; and the like.
At least one or more femto cells are able to configure a femto cell group in a manner of being grouped per specific service or region. For instance, a femto cell group, to which an access to a specific terminal only is granted, can be called a closed subscriber group (CSG). And, a femto base station (FBS) is able to grant an access to a terminal having subscribed to the CSG only by checking a CSG identification (CSG ID) of the terminal.
FIG. 1 is a diagram for one example of a femto cell arranged structure in an overlay network.
Referring to FIG. 1, a backbone network of a femto cell base station is directly connected to a wired ISP network. And, a femto cell gateway (FGW) can exist at a connected point with the ISP network. The FGW is able to play a role as a contact point for connecting a communication with a macro base station (MBS).
The FGW can be directly connected to femto cell base stations (FBSs) or can be situated in a concept of an integrated server between a core network and the IPS network. And, a system is able to secure the communication with a macro BS via CNS SW and ASN GW irrespective of a location of the FGW. In an overlay network, MBS is able to transmit/receive or store informations on femto base stations (FBSs) entirely or in part.
After a femto cell BS configuration has been completed, the MBS is able to recognize information including the location information of the FBS. Therefore, the MBS is able to directly perform wireless interface communication (i.e., air-interface communication) with the FBS.
In this case, a macro base station including a home femto BS and a CSG (closed subscriber group) femto base station can be called an overlay macro base station (overlay macro BS).
FIG. 2 is a diagram for one example of a femto cell arrangement structure in a non-overlay network.
In case that many users temporarily exist on adjacent boundaries of MBSs in a non-overlay structure, FBSs can be installed on a boundary of a macro cell. In this case, the MBS may not store all informations of the FBSs. If so, FGW is able to play a role as a contact point for connecting a communication with the MBS like the overlay structure.
In the following description, an idle mode of a terminal and a paging group in association with embodiments of the present are schematically explained.
First of all, an idle mode generally means the operation for helping a terminal to periodically perform a DL (downlink) broadcast traffic transmission without registering at a specific base station when the terminal moves in a radio link environment configured with multiple base stations.
In case that a terminal fails in receiving a traffic from a base station for a predetermined duration, it is able to make a transition to an idle mode to save power (i.e., for power saving). Having make the transition to the idle mode, the terminal receives a broadcast message (e.g., a paging message) transmitted by the base station and is then able to determine whether to make a transition to a normal mode or to remain in the idle mode. Moreover, the terminal in the idle mode performs a location update to inform a paging controller of its location.
The idle mode can benefit the terminal in a manner of eliminating an activation request associated with handover and general operation requests. The idle mode restricts a terminal activity to be scanned in a discrete cycle, thereby saving a power and operational resource used by the terminal.
The idle mode provides a terminal with a simple and proper scheme of announcing a pending downlink traffic. And, the idle mode is able to benefit a network and a base station in a manner of eliminating radio interface and network handover (HO) traffics from an inactive terminal.
Paging means a function of obtaining a location (e.g., a prescribed base station, a prescribed switching center, etc.) of a mobile station (MS) corresponding to an incoming call generation in a mobile communication. A plurality of base stations (BSs) capable of supporting idle mode can configure a paging region by belonging to a specific paging group.
In this case, the paging group indicates a logical group. The object of the paging group is to provide an adjacent range region, which can be paged in downlink (DL), if there is a traffic that targets a mobile station (MS). The paging group preferably meets a condition that the paging group is sufficiently big enough to enable a specific terminal to exist for most of time within the same paging group and a condition that a paging load should be sufficiently small to maintain a proper level.
A paging group is able to include at least one base station. And, one base station can be included in at least one or more paging groups. A paging group is defined by a management system. In the paging group, a paging group-action backbone network message. A paging controller manages a list of terminals in idle mode using a paging-announce message that is one of backbone network messages. And, the paging controller is able to manage the initial paging of all base stations belonging to a paging group.
In order to raise a hit ratio of paging, a terminal is able to perform a location update procedure. In this case, the location update is an operation of a terminal to raise the hit ratio of the paging to a terminal having entered an idle mode and indicates a process for a terminal to report a new location or region, which is entered by the terminal moves on moving away into a new region, to a network. Such a location update procedure can be performed in a manner that a ranging request (RNG-REQ) message and a ranging response (RNG-RSP) message are exchanged between a terminal and a base station.